1. Field of the Invention
This invention relates to a method for forming hook engaging parts in terminal parts of materials for the vertical suspension type surface treatment while the materials are in transit to a framing station. More particularly, this invention relates to a method for forming in the terminal parts of the materials such hook engaging parts as to be engaged with nipping devices of a carrier bar serving to convey the materials as vertically suspended therefrom successively through a series of surface-treating baths.
2. Description of the Prior Art
It is widely known that as a measure to surface-treat such long materials as extruded profiles of aluminum, the method of vertical suspension type surface treatment which comprises vertically suspending materials under treatment from a carrier bar 1 provided at the opposite terminal parts thereof with electrode contacts 2 as illustrated in FIG. 1 and causing the carrier bar to convey the materials successively through a series of surface-treating baths such as degreasing bath, rinsing bath, and electrolytic bath and dip them severally in these surface-treating baths to consequently form an anodic oxide film and a colored oxide film thereon has been developed and adopted for actual use. Heretofore, since the work of attaching the materials yet to be treated to the carrier bar 1 on the loading side for supplying the materials has consisted of attaching suspending jigs capable of nipping a given object after the fashion of a clip, one each to the materials under treatment, and then hooking the suspending jigs one each on the conducting bars disposed on the lower surface of the carrier bar 1 along the longitudinal direction thereof, it necessitates appreciable amounts of time and labor. Further this work is extremely complicate and is deficient in efficiency because it is destined to handle a large number of materials. Thus, for a plant specializing in surface treatment, the work has constituted itself a major obstacle to the series of rationalizing steps taken to fulfill the most important tasks of saving labor and enhancing efficiency.
Further, the work of racking the materials under treatment by the use of the conventional suspending jigs has consisted solely in causing the suspending jigs to take hold of these materials by nipping their leading terminal parts after the fashion of a clip, it entails the possibility of the seized materials accidentally slipping off the suspending jigs when the carrier bar is raised upright to suspend the materials in a vertical direction or when the carrier bar is raised or lowered for the purpose of conveyance to the surface-treating baths or immersion in the baths. The fact that the suspending jigs are incapable of generating an ample nipping and retaining force possibly entails the phenomenon of impairing electric conduction during the electrolytic treatment.
For the purpose of solving these problems, Japanese Patent Publications No. 55-6119 (6,119/1980) and No. 55-6120 (6,120/1980) propose a method for racking the materials under treatment by forming a notch 12 in the terminal part of each material 11 under treatment in mid course of the conveyance on a conveyor disposed immediately in front of a framing station and causing a hooking part 6 formed at the leading terminal of a depressing member 5 (or a supporting plate 4) of a material nipping device (suspending jig) 10 to be hooked in the notch 12 as illustrated in FIG. 2. The teachings of said patent literatures are hereby incorporated by reference. To be specific, as illustrated in FIG. 1 and FIG. 2, for example, the racking of the material 11 under treatment on a carrier bar 1 is performed by using a nipping device (suspending jig) 10. The suspending jig 10 comprises a conductive supporting plate 4 whose upper end is nipped and secured between the lower terminal parts of a pair of L-shaped suspending metal pieces 3, 3 attached fast to the lower surface of the carrier bar 1, a supporting member 7 provided projectingly on the supporting plate 4, and a depressing member 5 rotatably attached through the medium of an axial pin 9 to the leading terminal part of the supporting member 7, the leading terminal of the depressing member 5 being bent to form a hooking part 6. The retention of the material 11 by the suspending jig 10 in the nipped state is effected by allowing the hooking part 6 to be engaged with the notch 12 of the material 11 and causing the hooking part 6 of the depressing member 5 to be pressed against the supporting plate 4 by means of a spring 8 adapted to interconnect the depressing member 5 and the supporting plate 4.
The patent publications mentioned above further disclose a racking apparatus which is capable of automatically racking the materials under treatment to the carrier bar 1 by leveling down the carrier bar 1 toward the loading side for supplying the materials 11 under treatment, causing the notch 12 to be formed in the terminal part of the material 11 while the material is in transit in the lateral direction toward the carrier bar 1, allowing the hooking part 6 at the leading terminal of the depressing member 5 of the nipping device 10 fixed to the carrier bar 1 to engage with the notch 12, then raising the carrier bar 1 upright by a tumbler lifter, and loading it on the conveyor. The materials 11 suspended by the carrier bar 1 are forwarded by the conveyor successively to the series of surface-treating steps such as the step for rinsing with water and the step for electrolysis.
The racking method disclosed in said Japanese Patent Publications No. 55-6119 and No. 55-6120 indeed fulfill the requirement for enhancing the efficiency of the racking work and preventing the possible accidental fall of the materials under treatment. The mere automation of the racking step, however, does not always lead to full automation of the whole operation ranging from the step of extrusion through the step of surface treatment. The racking step, therefore, requires automation which is incapable of obstructing the flow of operation from the stop of extrusion through the step of surface treatment.
The automation of the racking step dictates the precondition of ensuring racking of materials of varying sizes all together and allowing insertion of suitable intervals between the materials proportionately to their sizes (peripheral length, height, and width) for the sake of uniformizing the thicknesses of an oxide film and an applied coating and the coloration in the course of the surface treatment and, therefore, allowing free alteration of the pitch between the adjacent materials suspended by the carrier bar. The necessary alteration in the pitch during the conveyance of materials on the conveyor to the framing station necessitates a method for varying the speed of both or either of the feed conveyor and the arranging conveyor. To be specific, the automation of the racking operation requires (A) adjustment to the pitch designated for the materials of a particular shape, (B) adoption of a jig mechanism capable of allowing free alteration in the pitch, and (C) fabrication of the materials in the particular shape fit therefor.
The racking method disclosed in Japanese Patent Publications No. 55-6119 and No. 55-6120 mentioned above fulfills the requirements (A) to (C) mentioned above as the preconditions for the automation of the racking step and avoids accidental fall of the materials under treatment and, therefore, is incapable of entailing various problems due to the unexpected fall of a material (when a material is suffered to fall into any of the baths in the line of surface-treating process, it will remain upright or aslant in the bath and stand in the way of subsequent materials being conveyed along the line of process).
In the method disclosed in the patent publications mentioned above, however, the formation of the notch in the material is accomplished by the operation of a rotary blade performed on the material being temporarily seized with a seizing device at a point along the length of the conveyor. Thus, the automation of the entire line of operation is difficult to attain because this formation of the notch interferes with the flow of the line from the step of extrusion through the step of surface treatment.
Since the work of forming the notch in the material is carried out at the framing station of the raw material station preceding the supply of materials to the framing station, it has the problem of producing chips from the formation of the notch in the material and consequently suffering the chips to adhere to the material and inflict damage thereto, inducing scatter of chips during the erection of the carrier bar with the tumbler lifter, and consequently suffering the chips to drift and jeopardize the work environment and further suffering the chips to fall into and pile up in the baths (as for degreasing and rinsing with water) in the line of operation and consequently degrade the quality of the baths.
The aforementioned method further has the problem of being unable to frame materials of the shape of a flat or a strip because the rotary blade is incapable of inserting a notch in such materials.